I have a 10 gallon that I will finally be tearing down because the snail population exploded and I wanted to replace the tank with a Amanzonian II based experimental tank.
I tried all the following things without much success.
(1) reduced feeding. Lol, there was never a overfeeding issue. I had one oto that got fed a piece of zucchini every other day.
(2) The Zucchini that was used to feed the oto was also used to bait the snails. But the method did not sufficiently reduce their numbers. Every week during 50% weekly water changes, I saw literally dozens of baby ones in my filter and filter media.
I thought of a using had-a-snail treatment, but read that the copper sulphite in it could do more harm than good. The last thing that I wanted to was kill the oto in the tank in my attempts to kill the snails. I could have got a snail eating fish which I seriously thought about, but considering the tank also suffers from chronic green dust algae and green spot algae despite high plant density, consistent c02 injection, excel treatment, and EI fert dosing, it is a good time to tear the tank down. Also, I have to make room for the Amazonian II aquasoil based experimental tank.
I learned my lesson, all plants that I purchase from now will get a good alum+water soak for 3 days. I read that Jungle Clear Water had Potassium Permanganate and plants soaked in one gallon of water with 1 table Jungle Clear would be enough to kill snails and snail eggs. Lol, it did not work, even at 3 tablets per gallon, which leads me to conclude that while a Potassium Permanganate and water solution for plants may kill snails and snail eggs, there is not likely a sufficient concentration of Potassium Permanganate in the Jungle Clear tablets to get the job done. I still had snails emerge after soaking the plants with the Jungle Clear and water solution. Stick to a 3 day soak with Alum and water or even go with 1 part bleach and 19 parts water solution if you cannot get your hands on Potassium Permanganate cocentrated powder.